According to a CDMA radio transmission method, in a cellular method dividing a service area into a plurality of cells and arranging a base station at the center of each cell, transmission is performed by dividing one cell into plural areas referred to as a sector and arranging an antenna for each sector. Upon performing so-called soft-handover that the mobile terminal performs communication through more than one sector concurrently with the base station (strictly, softer-handover is distinguished from the soft-handover performing simultaneous communication through the plural cells, however, they are not particularly distinguished from each other in this specification), the base station spreads the same symbol data simultaneously with different spread codes and transmits them from the plural antennas to each sector. This increases the amount of interference between transmission signals in each sector (or a cell) and as a result, the number of users admitted in a sector is reduced.
By performing a site selection diversity power control (SSDT: Site Selection Diversity Transmit Power Control) upon the soft-handover, it is possible to suppress the increase of the interference occurred due to transmission of the same data to the plural sectors (or cells). In addition, by the SSDT, a high-speed site selection can be performed without increasing the load of the network due to the site selection control via a network. In the SSDT, the output states of the plural antennas transmitting the same data are changed, so that it is necessary to change over the transmission state of a spreader corresponding to each antenna into the output state or the stop state.
In order to perform the high-speed site selection, it is necessary for the SSDT to change the transmission state of the spreader in units of slot or symbol. In addition, this operation is performed for each of plural spread processing parts at a transmission part. Accordingly, it is feared that the processing is delayed due to increase of the number of processing calls and a generation rate of the handover.
As an example of the configuration of a transmission spread processing part in a communication base station in a conventional CDMA method, the configuration that the number of the antenna is three is shown in FIG. 1. With reference to FIG. 1, the transmission spread processing part is configured by an encode processing part 1, a spread part 2, radio transmission processing parts 3a to 3c, and antennas 4a to 4c. The spread part 2 is configured by a data separating part 201, a CPU 202, spread processing part groups 203a to 203c, and additively combining circuits 208a to 208c. 
The spread processing part group 203a has a plurality of spread processing parts having the same configurations and corresponding to users and each spread processing part is made of a spread processing circuit 205a. In addition, the spread processing part group 203b also has a plurality of spread processing parts having the same configurations and corresponding to users and each spread processing part is made of a spread processing circuit 205b. Further, the spread processing part group 203c also has a plurality of spread processing parts having the same configurations and corresponding to users and each spread processing part is made of a spread processing circuit 205c. 
The encode processing part 1 generates a transmission baseband signal and transmits it to the spread part 2. The spread part 2 performs the data separation with the data separating part 201 and inputs the transmission baseband signal that is separated to the spread processing part groups 203a to 203c therein. The spread processing circuit 205a performs the spread processing of the transmission baseband signal with a spread code for a transmission destination antenna 4a that is set by the CPU 202 and outputs the transmission spread signal to the additively combining circuit 208a. The additively combining circuit 208a additively combines each transmission spread signal from a plurality of spread processing circuits 205a and provides it to the corresponding radio transmission processing part 3a. 
The spread processing circuit 205b performs the spread processing of the transmission baseband signal with the spread code for a transmission destination antenna 4b that is set by the CPU 202 and outputs the transmission spread signal to the additively combining circuit 208b. The additively combining circuit 208b additively combines each transmission spread signal from a plurality of spread processing circuits 205b and provides it to the corresponding radio transmission processing part 3b. In the same way, the spread processing circuit 205c performs the spread processing of the transmission baseband signal by using the spread code for a transmission destination antenna 40 that is set by the CPU 202 and outputs the transmission spread signal to the additively combining circuit 208c. The additively combining circuit 208c additively combines each transmission spread signal from a plurality of spread processing circuits 205c and provides it to the corresponding radio transmission processing part 3c. 
The radio transmission processing parts 3a to 3c perform the orthogonal modulation, the radio frequency conversion, and the transmission power control with respect to the inputted transmission spread signals, and then, transmit them to the antennas 4a to 4c, respectively, as radio transmission signals. The antennas 4a to 4c radiation transmits the inputted radio transmission signals.
Here, the output state control of the spread processing part groups 203a to 203c is performed by the software processing with the CPU 202 in such a manner that spread processing parameters such as spread codes or the like in the spread processing circuits 205a to 205c are set or unset. In order to perform the transmission output control at the designated timing, in the software processing, a counter is provided and if a counter value becomes the designated counter value, the control of the spread processing circuits 205a to 205c is performed.
The transmission spread processing part shown in FIG. 1 involves a problem such that, if the frequency of use (a rate of operation) of the spread processing part is increased due to increase of calling and increase of the handover generation rate, the delay of the SSDT processing is caused due to increase of the software processing and this makes it impossible to change over the site instantaneously.